Carbon dioxide

A pulse oximeter can cause a false sense of security by giving a good saturation figure when someone's breathing is completely inadequate. This is especially true when a patient is getting supplementary oxygen.

There are two main functions of breathing, one is getting oxygen out of the air and into the body, the other is getting carbon dioxide out of the body and into the air. It possible for someone to be getting enough oxygen into their body but not be getting rid of enough carbon dioxide.

Oxygen saturation by itself does not tell the whole story about breathing - this is especially true if someone is being given oxygen. As a minimum it is also necessary to record the respiratory rate, and if they are having oxygen, how much they are having.